textproduct: Quad Cities

KEY MESSAGES

- Heat and humidity will continue to build over the area for much of this week, with heat indices of 95 to 105 degrees area-wide. Tuesday through Thursday look to be the hottest days of the week. A Heat Advisory remains in effect for areas along/south of I-80 through Thursday.

- The Storm Prediction Center continues to have a Marginal Risk, level 1 of 5, of severe storms for Tuesday for areas north of Highway 30. Damaging winds are the primary risk, with hail a secondary threat. The severe storm risk for late tonight has decreased, with the Marginal Risk no longer in effect.

- There is a near-daily risk of showers and storms possible more likely for areas along and north of I-80.

SHORT TERM /THROUGH TUESDAY/

Issued at 238 PM CDT Mon Aug 31 2026

The heat is on for much of this week, as a strong heat dome continues to build over the central CONUS. This heat dome is characterized by very strong 500 mb height anomalies, with the LREF ensemble cluster analysis remaining in very good agreement on 500 mb heights of 594 decameters over the southern Plains/southern MS River Valley regions. These values are around the 99th percentile of the NAEFS 500 mb height climatological percentiles. As of this writing , the latest observed heat indices for areas along and south of I-80 this afternoon are in the middle to upper 90s (even a few 100s), so we are well underway for this period of heat and humidity this week.

One change that has been made with this forecast package is a decreasing risk of strong to severe storms as the Storm Prediction Center has pulled the Marginal Risk (level 1 of 5) out of our forecast area entirely for today/tonight, so confidence is increasing that any storms that do occur will be non-severe. Really, the latest CAMs don't show much in the way of any showers or storms through Tuesday morning, so it seems more likely for much of the CWA to be dry, if not the entire CWA. Per the 31.12z REFS ensemble composite reflectivity paintball plots, worst case scenario would be an isolated shower or storm grazing our northwestern CWA by sunrise Tuesday, but only a few ensemble members even hint at this.

As we look to Tuesday, not much change in the forecast with regards to the heat and humidity. We do see a signal in the 31.12z HREF for 70-90% exceedance probabilities of 100+ degree heat indices for Bureau and Putnam counties in Illinois, so we have issued a Heat Advisory for these counties for Tuesday. The remainder of the advisory remains unchanged in terms of coverage. However, there has been an expansion in terms of time. More on that in the Long Term forecast section below. Now, as far as severe weather is concerned, we are still watching the potential for some activity to develop ahead of an approaching mid-level shortwave trough on the edge of the heat dome. Significant instability appears to be in place, with SBCAPE values around 2500 to 3500 J/kg across our north, along with deep-layer shear values around 30 to 40 knots. Lapse rates appears to be pretty meager, however, and the general forcing from the shortwave appears to be weak (looks stronger farther north in Wisconsin and Minnesota). With this said, there is enough of a signal for SPC to continue the Marginal Risk north of Highway 30, so we will need to keep an eye on any isolated severe storms in the afternoon/evening hours Tuesday.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 238 PM CDT Mon Aug 31 2026

The high heat and humidity continues through at least Thursday. Confidence in the hot conditions Wednesday through Thursday remain high, given the latest ECMWF EFI/Shift of Tails values for high temperatures are in excess of 0.8 to 0.9 (even some values over 0.95 in isolated spots), along with Shift of Tails values around 1. This suggests high confidence in anomalously warm high temperatures, although not extreme values based on the lower Shift of Tails. With the potential for these anomalously hot conditions to last this week, we've decided to extend the Heat Advisory another day (through Thursday). It's entirely possible for the advisory to be extended into Friday, given LREF ensemble exceedance probabilities of 100 degree heat indices exceeding 50% across our southern two tiers of counties. Additionally, overnight lows might not dip below 75 degrees Tuesday night through Wednesday night, so this would compound the heat stress - even at night. There is potential for some record warm low temperatures during this period. See the Climate section below for the current records.

In terms of thunderstorm activity for mid- to late-week, with the strongest part of the heat building for Wednesday, seems like the storm track will stay to our north. However, there is a signal for the edge of the heat dome to sink slightly southward Thursday and Friday, generating more active conditions during this time frame. NBM consensus model blends seem to keep the chances of precipitation north of the I-80 corridor (20-50% chances) for Thursday and Friday, so the extreme heat could still be in play, even into Friday. Uncertainty remains on the impact this activity will have on the heat potential for the northern forecast area, so stay tuned for updates throughout the week!

A look ahead to the upcoming weekend: the heat appears to diminish by the weekend, although there are some signals it will be more active, with additional chances of showers and storms. In terms of severe weather, this potential appears to be pretty low, given the lower probabilities from the various machine-learning severe prob resources.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1246 PM CDT Mon Aug 31 2026

VFR conditions should be common over the area throughout the TAF period. The only exception will be over the next one to two hours at DBQ where a small area of weak thunderstorms has developed, which could bring MVFR visibility reductions due to rain. Outside of this, we're not seeing much of a signal for additional showers or storms (at least until Tuesday afternoon/evening). Southwesterly flow around 10 knots will continue through sunset this evening before becoming light and variable overnight into Tuesday morning.

CLIMATE

Issued at 222 PM CDT Sun Aug 30 2026

Record Warm Low Temperatures:

August 31: KDBQ: 74/2000 KMLI: 75/2000

September 1: KDBQ: 73/1937 KMLI: 75/1913

September 2: KDBQ: 74/2011 KMLI: 77/1913

September 3: KDBQ: 73/1939 KMLI: 76/1939

September 4: KDBQ: 71/1912 KMLI: 74/2018

DVN WATCHES/WARNINGS/ADVISORIES

IA...Heat Advisory until 7 PM CDT Thursday for IAZ063>065-067-068- 076>078-087>089-098-099. IL...Heat Advisory until 7 PM CDT Thursday for ILZ015-016-024>026- 034-035. Heat Advisory from 1 PM Tuesday to 7 PM CDT Thursday for ILZ017-018. MO...Heat Advisory until 7 PM CDT Thursday for MOZ009-010.